Sorry to insist, but whatever the emissions of your 3 liter engine the ones from (for instance) SMART car from Daimler are for sure considerably lower. Just imagine if all americans with 3 liter and more powerful engines would just drive the SMART car... can you imagine the impact this would have on the environment???
This car can easily cruise at 55 mph, so I guess there is no argument considering the performance..maybe capacity could be an issue since it has just two seats (but in this case you could drive a hyunday Matiz, for instance...)
In Europe SMART car is very popular due to low consumptions (1 liter of premium here costs $1 US. I insist: one liter, not one gallon...) and obvious advantages when parking on "crowded" towns.